Engine stop control system for vehicle

ABSTRACT

When the shift position is an N position or a P position during deceleration of a vehicle, or when a brake pedal is depressed even if the shift position is a D position or an R position, an engine E is stopped to prohibit an unnecessary idling operation by prohibiting the restarting of the supplying of fuel subsequent to the fuel cut by a command from an electronic control unit. If the supplying of fuel is restarted when the engine is in stoppage, a starter motor is driven automatically to start the engine. Thus, in a vehicle including an automatic transmission, the time of stoppage of the engine can be prolonged as much as possible in a range in which the operability of the vehicle is injured, thereby providing a reduction in amount of fuel consumed.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an engine stop control system for avehicle in which when a predetermined condition is established during anidling operation, an engine is stopped to reduce the amount of fuelconsumed.

2. Description of the Related Art

A conventional vehicle using an engine as a traveling drive sourcesuffers from a problem in that the engine once started is not stoppedunless a driver turns an ignition switch off and for this reason, thewasteful idling operation of the engine is continued for asignal-waiting period, for example, thereby consuming fuel wastefully.To avoid this, the driver may turn the ignition switch off to stop theengine every time the vehicle is stopped. In this case, however, thedriver must repeatedly carry out the starting and the stopping of theengine and hence, such operation is extremely troublesome.

Therefore, in a commercially available vehicle including a manualtransmission mounted therein, an engine is stopped automatically after alapse of 1 to 2 seconds from the stoppage of the vehicle. If thedepression of a clutch pedal from this state is detected, the engine isrestarted automatically, thereby providing a reduction in the amount offuel consumed.

In the conventional vehicle, however, the engine is stopped only for aperiod from a time point after the lapse of 1 to 2 seconds from thestopping of the vehicle to a time point of the depression of the clutchpedal. Therefore, to further reduce the amount of fuel consumed, it isdesired that the time of stoppage of the engine is prolonged as much aspossible in a range in which the operability of the vehicle is notdiminished.

If the engine is turned off upon stopping of the vehicle and thenrestarted upon starting of the vehicle, as described above, thefollowing problem is encountered: When the stopping and starting of thevehicle are repeatedly carried out at short time intervals on a road inwhich there is a traffic jam, the stopping and restarting of the engineare carried out frequently and hence, the driver may become irritated.

SUMMARY OF THE INVENTION

Accordingly, it is a first object of the present invention to ensurethat in a vehicle including an automatic transmission, the time ofstoppage of the engine is prolonged as much as possible in the range inwhich the operability of the vehicle is not diminished, therebyproviding a reduction in the amount of fuel consumed.

It is a second object of the present invention to ensure that in avehicle including a manual transmission, the time of stoppage of theengine is prolonged as much as possible to provide a reduction in amountof fuel consumed, while the stopping and restarting of the engine areprevented from being carried out frequently in a traffic jam.

To achieve the above first object, according to a first aspect andfeature of the present invention, there is provided an engine stopcontrol system for a vehicle, comprising an engine, an automatictransmission for transmitting a driving force of the engine to drivenwheels, a shift position detecting means for detecting a shift positionof the automatic transmission, a braking operation detecting means fordetecting a braking operation provided by a driver, a fuel supplycontrol means for controlling the supply of fuel to the engine, adecelerated-state detecting means for detecting a decelerated state ofthe vehicle, and an engine output control means including a means forcutting off the supplying of fuel to the engine by the fuel supplycontrol means, when the decelerated state of the vehicle is detected bythe decelerated-state detecting means, and for restarting the supplyingof fuel to start the engine, when the number of revolutions of theengine is equal to or less than a threshold value, the engine outputcontrol means operating, after cutting-off of the supply of fuel by thefuel supply control means during deceleration of the vehicle, to restartthe supplying of fuel, if the number of revolutions of the enginebecomes equal to or less than the threshold value, when the shiftposition detected by the shift position detecting means is a travelposition and the braking operation is not detected by the brakingoperation detecting means after and stop the engine without restartingof the supply of fuel even if the number of revolutions of the enginebecomes equal to or less than the threshold value, when the shiftposition detected by the shift position detecting means is a non-travelposition, or when the shift position detected by the shift positiondetecting means is a travel position and the braking operation isdetected by the braking operation detecting means.

With the above arrangement, when the shift position is the travelposition and the braking operation is not detected, the driving of theengine is maintained. Therefore, the undesirable stopping of the enginecan be avoided, and the necessary idling operation of the engine can becarried out. When the shift position is the non-travel position, or whenthe shift position is the travel position and the braking operation isdetected, the engine is stopped. Therefore, the engine can be stoppedfor a maximum amount of time without carrying-out of the unnecessaryidling operation, thereby reducing the amount of fuel consumed.

The non-travel position used herein corresponds to a neutral positionand a parking position in one embodiment, and the travel positioncorresponds to a forward travel position and a backward travel positionin the embodiment.

To achieve the above second object, according to a second aspect andfeature of the present invention, there is provided an engine stopcontrol system for a vehicle, comprising an engine, a manualtransmission for transmitting a driving force of the engine to drivenwheels, a shift position detecting means for detecting a shift positionof the manual transmission, a clutch operation detecting means fordetecting the engaging/disengaging operation of a clutch pedal to carryout the cut-off and coupling of a driving force between the engine andthe manual transmission, a vehicle speed detecting means for detecting avehicle speed, a throttle opening degree detecting means for detecting athrottle opening degree, a decelerated-state detecting means fordetecting a decelerated state of the vehicle, and an engine outputcontrol means including a means for cutting off the supplying of fuel tothe engine by the fuel supply control means, when a decelerated state ofthe vehicle is detected by a decelerated-state detecting means, and forrestarting the supplying of fuel to start the engine, when the number ofrevolutions of the engine becomes equal to or less than a thresholdvalue, the engine output control means continuing the cutting-off of thesupplying of fuel, if the throttle opening degree detected by thethrottle opening degree detecting means is a fully-closed throttleopening degree, when the vehicle speed detected by the vehicle speeddetecting means reaches a predetermined vehicle speed; and when theclutch-disengaging operation is detected by the clutch operationdetecting means, and the shift position detected by the shift positiondetecting means is a non-travel position, after cutting-off of thesupplying of fuel by the fuel supply control means during decelerationof the vehicle, and restarting the supplying of fuel, if the throttleopening degree detected by the throttle opening degree detecting meansis not the fully-closed throttle opening degree.

With the above arrangement, after the vehicle speed detected by thevehicle speed detecting means reaches the predetermined vehicle speedafter starting of the vehicle, the engine is stopped if the throttleopening degree is the fully-closed opening degree, when theclutch-disengaging operation is detected and the shift position is thenon-travel position. Therefore, the engine can be stopped to the maximumwithout carrying-out of the unnecessary idling operation to reduce theamount of fuel consumed. Moreover, if the throttle opening degree is notthe fully-closed opening degree, the engine is not stopped. Therefore,it is possible to prevent the engine from being stopped, for example,when an accelerator pedal is depressed to carry out a downshiftingduring traveling of the vehicle, and an increase in the number ofrevolutions of the engine corresponding to the throttle opening degreecan be achieved to carry out the downshifting smoothly. In addition, thestopping of the engine is not carried out until the vehicle speedreaches the predetermined vehicle speed after starting of the vehicle.Therefore, it is possible to avoid repeated stopping and starting of theengine in a traffic jam or during garaging of the vehicle by creeping,thereby preventing the driver from feeling irritation.

The non-travel position used herein corresponds to a neutral positionand a parking position in one embodiment, and the travel positioncorresponds to a forward travel position and a backward travel positionin the embodiment. The above and other objects, features and advantagesof the invention will become apparent from the following description ofthe preferred embodiments taken in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 to 10 show a first embodiment of the present invention, wherein:

FIG. 1 is a view of the entire arrangement of a hybrid vehicle includingan automatic transmission;

FIG. 2 is a diagram for explaining a cruising/idling mode;

FIG. 3 is a diagram for explaining an accelerating mode;

FIG. 4 is a diagram for explaining a decelerating mode;

FIG. 5A is a diagram showing the vehicle speed V anddriving/regenerative quantity of a motor M, when the vehicle istraveling in a 10•15 mode;

FIG. 5B is a diagram showing the negative pressure of intake aircorresponding to the load of the engine E;

FIG. 6 is a view of the idle engine stop control system of the firstembodiment;

FIG. 7 is a first portion of a flow chart of a main routine;

FIG. 8 is a second portion of the flow chart of the main routine;

FIG. 9 is a flow chart of a sub-routine of Step S17 in the main routine;

FIG. 10 is a time chart showing one example of an idle engine stopcontrol operation;

FIGS. 11 to 15 show a second embodiment of the present invention,wherein

FIG. 11 is a view of the entire arrangement of a hybrid vehicleincluding a manual transmission;

FIG. 12 is a view of the idle engine stop control system of the secondembodiment;

FIG. 13 is a first portion of a flow chart of a main routine;

FIG. 14 is a second portion of the flow chart of the main routine; and

FIG. 15 is a time chart illustrating one example of an idle engine stopcontrol operation.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A first embodiment of the present invention will now be described withreference to FIGS. 1 to 10.

As shown in FIG. 1, a hybrid vehicle includes an engine E and a motor M.The driving force of the engine E and/or the driving force of the motorM is transmitted through an automatic transmission Ta to front wheelsWf, Wf, which are driven wheels. When the driving force is transmittedfrom the front wheels Wf, Wf, to the motor M during deceleration of thehybrid vehicle, the motor M functions as a generator to produce aso-called regenerative braking force and to recover a kinetic energy ofa vehicle body as electric energy.

The control of the driving and regenerative operations of the motor M iscarried out by a power drive unit 2 connected to an electronic controlunit 1 comprising a microcomputer. A capacitor 3 as an accumulatingmeans comprising an electric double-layer condenser is connected to thepower drive unit 2. The capacitor 3 comprises six modules connected inseries, with twelve cells connected in series and having a maximumvoltage of 2.5 V connected in series, and having a maximum voltage of180 V. An auxiliary battery 4 of 12 V for driving various auxiliaries ismounted in the hybrid vehicle and connected through a downverter 5 tothe capacitor 3. The downverter 5 controlled by the electronic controlunit 1 drops the voltage of the capacitor 3 to 12 V to charge theauxiliary battery 4.

The maximum voltage of the capacitor 3 is 180 V, but the maximum voltageactually used in order to prevent the deterioration due to overchargingis limited to 170 V, and the minimum voltage actually used in order toensure the operation of the downverter 5 is limited to 80 V.

The electronic control unit 1 controls the operation of a fuel supplycontrol means 6 for controlling the amount of fuel supplied to theengine E and the operation of a starter motor 7 driven by an electricpower accumulated in the capacitor 3, in addition to the power driveunit 2 and the downverter 5. For this purpose, the following signals areinputted to the electronic control unit 1: a signal from a vehicle speedsensor S₁ for detecting a vehicle speed V based on the rotational speedsof rear wheels Wr, Wr which are follower wheels; a signal from an enginerevolution-number sensor S₂ for detecting a number Ne of revolutions ofthe engine; a signal from a shift position sensor S₃ for detecting ashift position (such as a neutral position, a parking position, aforward travel position and a backward travel position) of the automatictransmission Ta; a signal from a brake switch S₄ for detecting theoperation of a brake pedal 8; a signal from a capacitor remainingcapacity sensor S₇ for detecting a remaining capacity of the capacitor3; a signal from a 12-Volt consumed-power sensor S₈ for detecting aconsumed power taken out of auxiliary battery 4; a signal from anignition switch S₉; and a signal from a starter switch S₁₀.

The electronic control unit 1 includes a decelerated-state detectingmeans M1 and an engine output control means M2 (see FIG. 6). Thedecelerated-state detecting means M1 detects that the vehicle is in adecelerated/fuel-cut state, based on a variation in vehicle speed Vdetected by the vehicle speed sensor S₁, the closing motion of athrottle valve detected by a throttle opening degree sensor, a negativepressure of intake air detected by intake-air negative pressure sensorand the like. The engine output control means M2 is adapted to cut offthe amount of fuel supplied to the engine E by the fuel supply controlmeans 6 to stop the engine E.

An outline of the control of the engine E and the motor M in each oftravel modes will be described below.

(1) Cruising/idling Mode

As shown in FIG. 2, during cruising of the vehicle or during idlingoperation of the engine E, the motor M functions as a generator drivenby the engine E. A consumed power taken out of the auxiliary battery 4of 12 V is estimated from an electric power upstream of the downverter5, and an electric power enough to be able to replenish the 12-voltconsumed power is generated by the motor M and supplied to the auxiliarybattery 4.

(2) Accelerating Mode

As shown in FIG. 3, during accelerating travel of the vehicle, the motorM is driven by an electric power taken out of the capacitor 3 to assistin the output of the engine E and to replenish the 12-volt consumedpower taken out of the auxiliary battery 4. The assisting amountgenerated by the motor M is determined by map-searching, based on theremaining capacity of the capacitor 3, the shift position, the number ofrevolutions of the engine, the throttle opening degree, the negativepressure of intake air and the like.

(3) Decelerating Mode

As shown in FIG. 4, during decelerating travel of the vehicle, theregenerative braking operation is carried out by the driving forcereversely transmitted from the front wheels Wf, Wf which are drivingwheels to the motor M. The capacitor 3 is charged by the regenerativepower generated by the motor M, and the 12-volt consumed power taken outof the auxiliary battery 4 is replenished. The regenerative brakingquantity generated by the motor M is determined by map-searching basedon the shift position, the number of revolutions of the engine and thenegative pressure of intake air.

FIG. 5A shows the vehicle speed V (see a thin line) and thedriving/regenerative quantity (see thick line), when the vehicle travelsin a 10•14 mode. During accelerating travel of the vehicle, the motor Mgenerates a driving force to alleviate the load of the engine E, wherebythe amount of fuel consumed can be reduced. During decelerating travelof the vehicle, the motor M generates a regenerative braking force, andthe kinetic energy lost intrinsically by the mechanical brakingoperation can be effectively recovered as electric energy.

FIG. 5B shows the negative pressure of intake air corresponding to theload of the engine E, wherein a thick line corresponds to a case wherethe assisting by the motor M was carried out, and a thin linecorresponds to a case where the assisting by the motor M was not carriedout. Generally, the thick line lies below the thin line, and it can beseen that the assisting force of the motor contributes to thealleviation of the load of the engine E.

The typical vehicle is designed so that the fuel is cut duringdeceleration of the vehicle, and when the number of revolutions of theengine is decreased to an idling level, the fuel cut is discontinued, sothat the engine E is not stopped, and the supplying of the fuel in anamount enough to maintain the idling operation is restarted. In thisembodiment, however, when a predetermined operating condition isestablished, the engine E is stopped without restoring of the fuelsupply subsequent to the fuel cut. When the predetermined operatingcondition is not established, the restoring of the fuel supply iscarried out to restart the engine, whereby the engine is stopped amaximum amount of time during idling operation to provide a furtherreduction in amount of fuel consumed.

The arrangement of the idle engine stop control system according to thisembodiment will be described below with reference to FIG. 6.

The fuel supply control means 6 controls the supplying of the fuel tothe engine E driving the front wheels Wf, Wf through the automatictransmission Ta on the basis of a command from the electric control unit1. The electric control unit 1 determines whether the idling operationof the engine is permitted, or prohibited for stopping of the engine,based on the vehicle speed inputted from the vehicle speed sensor S₁,the shift position inputted from the shift position sensor S₃, thebraked state inputted from the brake switch S₄ and the remainingcapacity of the capacitor 3 inputted from the capacitor remainingcapacity sensor S₇. When the idling operation is permitted, the fuelsupply control means 6 permits the restarting of the fuel supplysubsequent to the fuel cut to enable the idling operation. When theidling operation is prohibited, the fuel supply control means 6prohibits the restarting of the fuel supply subsequent to the fuel cutto stop the engine E.

When the idling operation is permitted when it is detected that theengine E is in stopped based on the output from the enginerevolution-number sensor S₂, the starter motor 7 is driven, and theengine E is automatically started. However, immediately after theignition switch S₉ is turned on, the starter motor 7 is driven only whenthe starter switch S₁₀ is turned on. Therefore, when a driver does notintend to move the vehicle, the engine E is not needlessly started.

The particular content of the idle engine stop control of the vehicleshown in FIG. 1 will be described below with reference to flow charts inFIGS. 7 and 8.

First, when the starter switch S₁₀ is in a turned-off state at Step S1,i.e., when the engine starting operation is not carried out by thedriver, the state of a starter switch OFF→ON determining flag F_FCMGSTis determined at Step S2. The initial value of the starter switch OFF→ONdetermining flag F_FCMGST at the time when the ignition switch S₉ isturned on is “0” when the engine starting operation is carried out bythe driver at Step S1 to turn on the starter switch S₁₀, the starterswitch OFF→ON determining flag F_FCMGST is set at “1” at Step S15 andmaintained at “1”, until the ignition switch is turned off.

Therefore, the answer at Step S2 is “0” for a period from a time pointwhen the driver turns on the ignition switch S₉ to a time point when thedriver turns on the starter switch S₁₀, and the processing is advancedto Step S13 and hence, the starting of the engine at Step S12, whichwill be described hereinafter cannot be carried out. Namely, in thisvehicle, the stopping of the engine during the idling operation and thesubsequent starting of the engine are carried out, irrespective of theoperation of starter switch S₁₀ by the driver, as described hereinafter.However, unless the driver intends to turn on the starter switch S₁₀ tomove the vehicle, the engine E cannot be started automatically. Thus,the needless starting of the engine can be avoided to reduce the amountof fuel consumed.

If the driver turns on the starter switch S₁₀ at Step S1, the starterswitch OFF→ON determining flag F_FCMGST is set at “1” at Step S15, and abackward travel position determining delay timer tmSFTR which will bedescribed hereinafter is set at Step S16, shifting to Step S11. At StepS11, the number Ne of revolutions of the engine detected by the enginerevolution-number sensor S₂ is compared with an engine stall determiningrevolution-number NCR. If Ne<NCR to indicate that the engine E is in astopped state, the starter motor 7 is operated automatically to startthe engine E. As a result, when the engine E is started to ensure thatNe≧NCR, the starting of the engine at the Step S12 is passed,progressing to Step S13.

Subsequently, an idle engine stop control performing flag F_FCMG is setat “0” at Step S13. The idle engine stop control performing flag F_FCMGserves to determine whether the engine E is to be stopped during idlingoperation thereof. In a state in which the idle engine stop controlperforming flag F_FCMG has been set at “0”, the restarting of the fuelsupply subsequent to the fuel cut is carried out, causing the fuel to besupplied in an amount adequate enough to maintain the idling operationby the command from the engine output control means M2, whereby theengine E is maintained in the idling operation. In a state in which theidle engine stop control performing flag F_FCMG has been set at “1”, therestarting of the fuel supply subsequent to the fuel cut is prohibited(or the fuel is supplied in only an amount insufficient to maintain theidling operating) by the command from the engine output control meansM2, causing the engine E to be stopped without being idled. The idleengine stop control performing flag F_FCMG is set at “1” at Step S18,when a predetermined condition which will be described has beenestablished. At subsequent Step S14, a vehicle speed determining flagF_FCMGV is set at “0”.

Now, if the driver turns off the starter switch S₁₀ after turning-on ofthe starter switch S₁₀ to start the engine E, the starter switch OFF→ONdetermining flag F_FCMGST has been already set at “1” at Step S2 andhence, the processing is advanced to Step S3. If the shift positiondetected by the shift position sensor S₃ is not the backward travelposition at Step S3, the backward travel position determining delaytimer tmSFTR is set at Step S4. If the shift position is the backwardtravel position at Step S3, it is determined at Step S5 whether thecounting time of the backward travel position determining delay timertmSFTR is up, after elapse of a predetermined time (e.g., 0.5 seconds).As a result, if the backward travel position determining delay timertmSFTR is not up at Step S5, the processing is returned to Step S1. Ifthe backward travel position determining delay timer tmSFTR is up atStep S5, the processing is advanced to Step S11.

What this means is as follows: In the vehicle according to thisembodiment, if the driver releases his foot from the brake pedal 8, whenthe idle engine stop control is being carried out by depressing of thebrake pedal 8, the idle engine stop control is discontinued, causing theengine E to be restarted automatically. Suppose that the vehicleequipped with the automatic transmission Ta is allowed to creep backwardby repeating of the turning-on/off operation of the brake pedal 8, forexample, to garage the vehicle. In this case, if the engine isrepeatedly stopped and restarted every time the brake pedal 8 is tunedon and off, the following problem is encountered: it is difficult toensure smooth backward creeping. When the brake pedal 8 is depressed tochange the forward movement to the backward movement for garaging of thevehicle or the like, the engine E is stopped by the idle engine stopcontrol. Supposing that even if the shift position is changed to thebackward travel position, the engine E is not restarted unless thedriver releases his foot from the brake pedal 8, the following problemis encountered: backward creeping is not carried out smoothly.

In this embodiment, however, when the shift position is the backwardtravel position at Step S3, the processing is advanced to Steps S11 andS12. At this time, if the engine E is in stoppage, the engine isrestarted immediately, and at Step S13, the idle engine stop controlperforming flag F_FCMG is set at “0” to discontinue the idle engine stopcontrol. Therefore, the engine E can be maintained in the idlingoperation to solve the above problems. Moreover, if the time period forwhich the shift position is the backward travel position is not equal toor greater than 0.5 seconds counted by the backward travel positiondetermining delay timer tmSFTR, the above-described control is notcarried out. Therefore, it is possible to avoid that the unnecessarycontrol is carried out when the backward travel position has beenestablished instantaneously in the course of operation of a selectlever.

Subsequently, the state of the vehicle speed determining flag F_FCMGV isdetermined at Step S6. The vehicle speed determining flag F_FCMGV hasbeen set at “0” immediately after stating of the vehicle, and when thevehicle speed V detected by the vehicle speed sensor S₁ is equal to orpredetermined vehicle speed (e.g., 15 km/hr) at next Step S7, thevehicle speed determining flag F_FCMGV is set at “1” at Step S8.Therefore, unless the vehicle speed V is equal to or higher than 15km/hr at Step S7, the processing is necessarily advanced to Step S13, atwhich the idle engine stop control performing flag F_FCMG is set to “0”,whereby the idle engine stop control operation is discontinued andhence, cannot be carried out.

What this means is as follows: If the carrying-out of the idle enginestop control operation is permitted when the vehicle is allowed to creepat an extremely low speed for garaging of the vehicle or in a trafficjam, while turning on and off the brake pedal 8, the stopping andrestarting of the engine E are repeatedly carried out with theturning-on/off of the brake pedal 8, resulting in a possibility thatsmooth traveling of the vehicle cannot be achieved. However, the aboveproblem can be solved by prohibiting the carrying-out of the idle enginestop control operation when the vehicle speed V is lower than 15 km/hr.

If it is detected at subsequent Step S19 by the decelerated-statedetecting means M1 that the vehicle is in a decelerated state, theprocessing is shifted to Step S9. If the shift position is the neutralposition or the parking position at Step S9, or if the brake pedal 8 hasbeen depressed causing the brake switch S₄ to be turned on at Step S10,even if the shift position is the forward travel position at Step S9,the processing is advanced to Step S17, at which the state of acapacitor remaining-capacity determining flag F_FCMGCAP is determined.

The capacitor remaining-capacity determining flag F FCMGCAP is intendedto determine whether the remaining capacity of the electric poweraccumulated in the capacitor 3 is sufficient to restart the engine E. Ifthe capacitor remaining-capacity determining flag F_FCMGCAP has been setat “1” at Step S17, it is determined that the remaining capacity of thecapacitor 3 is sufficient to restart the engine E, and the processing isadvanced to Step S18, at which the idle engine stop control performingflag F_FCMG is set at “1”. As a result, by prohibiting the restarting ofthe fuel supply subsequent to the fuel cut by the fuel supply controlmeans 6 on the basis of the command from the engine output control meansM2, the engine E is stopped, when the number Ne of revolutions of theengine is decreased to the number of idling-revolutions of the engine.On the other hand, if the capacitor remaining-capacity determining flagF_FCMGCAP has been set at “0” at Step S17, it is determined that theremaining capacity of the capacitor 3 is not sufficient to restart theengine E, and at Step S13, the idle engine stop control performing flagF_FCMG is set at “0”. As a result, by restarting, as usual, the fuelsupply subsequent to the fuel cut by the fuel supply control means 6,the idling operation is permitted, when the number Ne of revolutions ofthe engine is decreased to the number of idling-revolutions of theengine.

When the shift position is the neutral position or the parking position,or when the brake pedal 8 has been depressed even if the shift positionis the forward travel position, as described above, the engine E isstopped without being idled. Therefore, unnecessary idling of the engineE can be minimized to reduce the amount of fuel consumed to the maximum.However, when the shift position is the backward travel position, whenthe vehicle speed V is less than 15 km/hr, and when the remainingcapacity of the capacitor 3 is not sufficient to restart the engine E,the carrying-out of the idle engine stop control operation isprohibited.

FIG. 10 is a time chart illustrating one example of the idle engine stopcontrol.

When the driver depresses the brake pedal to turn on the brake switch S₄at a time point t₁ during cruising of the vehicle, the idle engine stopcontrol performing flag F_FCMG is set at “1” and at the same time, thefuel cut is carried out by the fuel supply control means 6, whereby thevehicle speed V is gradually reduced. Even if the number Ne ofrevolutions of the engine is decreased to the number ofidling-revolutions of the engine at a time point t₂, the fuel supplycontrol means 6 does not restart the fuel supply, because the idleengine stop control performing flag F_FCMG has been set at “1”. As aresult, the engine E is stopped without being idled. When the driverreleases his foot from the brake pedal 8 to turn the brake switch S₄ offat a time point t₃, the idle engine stop control performing flag F_FCMGis set at “0” and at the same time, the fuel cut by the fuel supplycontrol means 6 is finished, and the fuel supplying is restarted. Thiscauses the engine E to be started, thereby enabling the vehicle totravel again.

The setting of the capacitor remaining-capacity determining flagF_FCMGCAP (see Step S17 in the flow chart in FIG. 7) will be describedbelow with reference to FIG. 9.

First, at Step S61, the number of revolutions of the engine detected bythe engine revolution-number sensor S₂ is compared with the engine stalldetermining revolution-number NCR. If Ne≧NCR to indicate that the engineE is in the operated state, a margin QCAPABL of remaining capacity ofthe capacitor 3 is calculated at Step S62 by subtracting the capacityQCAPIDL of the capacitor 3 required to start the engine E from theremaining capacity QCAP detected by the capacitor remaining-capacitysensor S7. Then, the 12-volt consumed power integration value DVPSUM isset at “0” at Step S63.

On the other hand, if the engine E is in the stopped state at Step S61,a current value DVPSUM of the 12-volt consumed power integration valueDVPSUM(n) is calculated by adding an instantaneous 12-volt powerconsumed-quantity value DVP (namely, an instantaneous value of powertaken out of the auxiliary battery 4) detected by the 12-volt consumedpower sensor S₈ to a last value of the 12-volt consumed powerintegration value DVPSUM(n−1). At Step S65, a result QDVP of conversionof the 12-volt consumed power integration value is calculated bymultiplying the 12-volt consumed power integration value DVPSUM(n)calculated at Step S64 by a unit conversion factor KDVP.

At subsequent Step S66, the margin QCAPABL of the remaining capacity ofthe capacitor 3 calculated at Step S62 is compared with the result QDVPof conversion of the 12-volt consumed power integration value calculatedat Step S65. When the engine E is stopped, the charging of the capacitor3 is not carried out, and the 12-volt consumed power (namely, the resultQDVP of conversion of the 12-volt consumed power integration value) istaken out of capacitor 3. Therefore, the remaining capacity QCAP of thecapacitor 3 is gradually decreased.

If the result QDVP of conversion of the 12-volt consumed powerintegration value is less than the margin QCAPABL of the remainingcapacity of the capacitor 3 at Step S66, i.e., if the remaining capacityQCAP of the capacitor 3 exceeds the capacity of the capacitor 3 requiredto start the engine E, it is determined that the engine E can be startedby the power of the capacitor 3, and at Step S67, the capacitorremaining-capacity determining flag F_FCMGCAP is set at “1” to permitthe carrying-out of the idle engine stop control operation. On the otherhand, if the result QDVP of conversion of the 12-volt consumed powerintegration value is equal to or greater than the margin QCAPABL of theremaining capacity of the capacitor 3 at Step S66, i.e., if theremaining capacity QCAP of the capacitor 3 is equal to or less than thecapacity of the capacitor 3 required to start the engine E, it isdetermined that there is a possibility that the engine E cannot bestarted, and at Step S68, the capacitor remaining-capacity determiningflag F FCMGCAP is set at “0” to prohibit the carrying-out of the idleengine stop control operation.

In this manner, the permission and prohibition of the carrying-out ofthe idle engine stop control operation are determined, while monitoringthe remaining capacity QCAP of the capacitor 3 driving the starter motor7. Therefore, the idle engine stop control operation can be carried outto the maximum to reduce the amount of fuel consumed, while reliablyavoiding that the remaining capacity QCAP of the capacitor 3 becomesinsufficient, whereby it is impossible to start the engine.

A second embodiment of the present invention will now be described withreference to FIGS. 11 to 15.

The hybrid vehicle according to the first embodiment shown in FIG. 1includes the automatic transmission Ta, whereas a hybrid vehicleaccording to the second embodiment shown in FIG. 11 includes a manualtransmission Tm. The following signals are inputted to an electroniccontrol unit 1 in the hybrid vehicle according to the second embodiment:a signal from a vehicle speed sensor S₁ for detecting a vehicle speed; asignal from an engine revolution-number sensor S₂ for detecting a numberNe of revolutions of the engine; a signal from a shift position sensorS₃ for detecting a shift position; a signal from a clutch switch S₅ fordetecting the operation of a clutch pedal 9; a signal from a throttleopening degree sensor S₆ for detecting an degree of opening of athrottle valve 10; a signal from a capacitor remaining-capacity sensorS₇ for detecting a remaining capacity of the capacitor 3; a signal froma 12-volt consumed power sensor S₈ for detecting a consumed powerbrought out of the auxiliary battery 4; a signal from an ignition switchS₉; and a signal from a starter switch S₁₀. Arrangements other than theabove-described arrangement are the same as in the first embodiment.

The arrangement of an idle engine stop control system according to thisembodiment will be described below with reference to FIG. 12 which.

The fuel supply control means 6 controls the supply of fuel to theengine E driving the front wheels Wf, Wf through the manual transmissionTm on the basis of a command from the electronic control unit 1. Theelectronic control unit 1 determines whether the idling operation of theengine E is permitted, or prohibited for stopping of the engine E, basedon a shift position inputted from the shift position sensor S₃, aclutch-disengaged state inputted from the clutch switch S₅, a vehiclespeed inputted from the vehicle speed sensor S₁, a throttle openingdegree inputted from the throttle opening degree sensor S₆, and aremaining capacity of the capacitor 3 inputted from the capacitorremaining-capacity sensor S₇. When the idling operation is to bepermitted, the fuel supply control means 6 permits the restarting of thefuel supply from the fuel cut by the command from the electronic controlunit 1 to enable the idling operation. When the idling operation is tobe prohibited, the fuel supply control means 6 prohibits the restartingof the fuel supply from the fuel cut to stop the engine.

The particular content of the idle engine stop control operation in thesecond embodiment will be described below.

First, when the starter switch S₁₀ is in a turned-off state at Step S21,i.e., when the engine starting operation is not carried out by a driver,the state of the starter switch OFF→ON determining flag F_FCMGST isdetermined at Step S22. The initial value of the starter switch OFF→ONdetermining flag F_FCMGST at a time when the ignition switch is turnedon, is “0”. Thereafter, when the engine starting operation is carriedout by the driver to turn on the starter switch S₁₀ at Step S21, thestarter switch OFF→ON determining flag F_FCMGST is set at “1” at StepS34, and maintained at “1”, until the ignition switch is turned off.

Therefore, the answer at Step S22 is “0” for a period from a time pointwhen the driver turns on the ignition switch to a time point when thedriver turns on the starter switch S₁₀, and the processing is advancedvia Step S23 to Step S33 and hence, the starting of the engine at StepS31 which will be described hereinafter cannot be carried out. Namely,in this vehicle, the stopping of the engine during the idling operationand the subsequent starting of the engine are carried out irrespectiveof the operation of starter switch S₁₀ by the driver, as describedhereinafter. However, unless the driver intends to turn on the starterswitch S10 to move the vehicle, the engine E cannot be startedautomatically. Thus, the wasteful starting of the engine can be avoidedto reduce the amount of fuel consumed.

If the driver turns on the starter switch S₁₀ at Step S21, the starterswitch OFF→ON determining flag F_FCMGST is set at “1” at Step S34, and avehicle speed determining flag F_FCMGV, which will be describedhereinafter, is set at “0” at Step S35, shifting to Step S30. At StepS30, the number Ne of revolutions of the engine detected by the enginerevolution-number sensor S₂ is compared with an engine stall determiningrevolution-number NCR. If Ne<NCR to indicate that the engine E is in astopped state, the starter motor 7 is operated automatically to startthe engine E. As a result, when the engine E is started to ensure thatNe≧NCR, the starting of the engine at the Step S31 is passed,progressing to Step S33.

Subsequently, the idle engine stop control performing flag F_FCMG is setat “0” at Step S33. The idle engine stop control performing flag F_FCMGserves to determine whether the engine E is to be stopped during idlingoperation thereof. In a state in which the idle engine stop controlperforming flag F_FCMG has been set at “0”, the restarting of the fuelsupply subsequent to the fuel cut is carried out, causing the engine Eto be maintained in the idling operation. In a state in which the idleengine stop control performing flag F_FCMG has been set at “1”, therestarting of the fuel supply subsequent to the fuel cut is prohibited,causing the engine E to be stopped without being idled. The idle enginestop control performing flag F_FCMG is set at “1” at Step S42, when apredetermined condition which will be described hereinafter has beenestablished.

Now, if the driver turns off the starter switch S₁₀ after turning-on ofthe starter switch S₁₀ to start the engine E, the starter switch OFF→ONdetermining flag F_FCMGST has been already set at “1” at Step S22 andhence, the processing is advanced to Step S24, at which the state of thevehicle speed determining flag F_FCMGV is determined. The vehicle speeddetermining flag F_FCMGV is set at “0” immediately after starting of thevehicle, and when the vehicle speed V detected by the vehicle speedsensor S₁ is equal to or higher than a predetermined vehicle speed(e.g., 15 km/hr) at next Step S25, the vehicle speed determining flagF_FCMGV is set at “1” at Step S26. Therefore, unless the vehicle sped Vis equal to or greater than 15 km/hr at Step S25, the processing isnecessarily advanced to Step S33, at which the idle engine stop controlperforming flag F_FCMG is set at “0”, whereby the idle engine stopcontrol operation is discontinued. Therefore, the idle engine stopcontrol operation cannot be carried out.

What this means is as follows: Suppose that when the traveling of thevehicle at a lower speed and the stopping of the vehicle are repeated atshort time intervals in a traffic jam or the like, the engine isrepeatedly stopped and restarted every time a shift lever is operatedbetween the neutral position and the forward travel position in a statein which the clutch pedal 9 has been depressed. In this case, there is apossibility that the smooth traveling cannot be achieved. However, theabove problem can be solved by prohibiting the carrying-out of the idleengine stop control operation, when the vehicle speed V is less than 15km/hr.

If it is detected at subsequent Step S43 by the decelerated-statedetecting means M1 that the vehicle is in a decelerated state, theprocessing is shifted to Step S27. If the clutch pedal 9 is notdepressed, whereby the clutch switch S₅ is in a turned-off state at StepS27, i.e., if the clutch is in an engaged state, the processing isadvanced to Step S37 to carry out the idle engine stop controloperation. If the clutch pedal 9 is depressed to turn the clutch switchS₅ on (in a clutch-disengaged state) at Step S27, and the shift positiondetected by the shift position sensor S₃ is the neutral position at StepS28, the processing is advanced to Step S36. If the throttle openingdegree detected by the throttle opening degree sensor S₆ is less than afully-closed throttle opening degree THIDLE at Step S36, the processingis advanced to Step S37 to carry out the idle engine stop controloperation.

On the other hand, even if the clutch switch S₅ has been turned on toprovide the clutch-disengaged state at Step S27, if the shift positionis an in-gear state (the forward travel position or the backward travelposition) at Step S28, the idle engine stop control operation is notcarried out, progressing to Step S29, at which an engine restartingdelay timer tmFCMG which will be described hereinafter is set. If theclutch switch S₅ has been turned on to provide the clutch-disengagedstate at Step S27, the shift position is the neutral position at StepS28 and further, the throttle opening degree TH is equal to or largerthan a fully-opened throttle opening degree THIDLE at Step S36, the idleengine stop control operation is likewise not carried out, progressingto Step S29.

What this means is as follows: The clutch-engaged state in which theclutch switch S₅ has been turned off, is a signal-waiting state or thelike, if the vehicle is in stoppage. Therefore, the frequency ofstoppage of the engine E can be increased to the maximum to provide areduction in amount of fuel consumed. If the shift position is theneutral position even in the clutch-disengaged state in which the clutchswitch S₅ has been turned on, it is likewise determined that the driverdoes not have an intention to move the vehicle. Therefore, the engine Ecan be likewise stopped to provide a reduction in the amount of fuelconsumed.

However, if the throttle opening degree TH is equal to or greater thanthe fully-closed throttle opening degree THIDLE at Step S36, i.e., ifthe driver has depressed an accelerator pedal, the idle engine stopcontrol operation is not carried out. This is because when thedownshifting is to be conducted in the vehicle including the manualtransmission Tm, the accelerator pedal may occasionally be temporarilydepressed to increase the number Ne of revolutions of the engine inorder to smoothly conduct the engagement of the clutch. In such a case,if the number Ne of revolutions of the engine E is not increased even ifthe accelerator pedal has been depressed, because the idle engine stopcontrol operation is being carried out, there is a possibility that thedownshifting operation is not carried out smoothly. In this embodiment,however, when the accelerator pedal is depressed, the idle engine stopcontrol operation is discontinued and hence, the number Ne ofrevolutions of the engine can be increased by depressing the acceleratorpedal to carry out the downshifting operation smoothly.

Suppose that the vehicle in the stopped state is to be started in astate in which the idle engine stop control operation is being carriedout. In this case, when the clutch pedal 9 is depressed and the shiftlevel is brought into the in-gear, the engine is started automatically,but if the accelerator pedal is depressed prior to such operation, theengine E can be started. Therefore, the engine E can be started beforeshifting into gear, thereby carrying out the starting of the vehiclesmoothly.

When the clutch switch 9 has been turned off at Step S27, or when thethrottle opening degree TH is less than the fully-closed throttleopening degree THIDLE at Step S36, the state of the capacitorremaining-capacity determining flag F_FCMGCAP is determined at Step S37,before the idle engine stop control operation is carried out.

The capacitor remaining-capacity determining flag F_FCMGCAP is intendedto determine whether the remaining capacity of the power accumulated inthe capacitor 3 is sufficient to restart the stopped engine E. If thecapacitor remaining-capacity determining flag F_FCMGCAP has been set at“1” at Step S37, it is determined that the remaining capacity of thecapacitor 3 is sufficient to restart the engine E. The restarting delaytimer tmFCMG which will be described hereinafter is set at Step S41 andthen, the idle engine stop control performing flag F_FCMG is set at “1”at Step S42. The setting of the capacitor remaining-capacity determiningflag F FCMGCAP is the same as the case described with reference to FIG.9 showing the first embodiment and hence, the duplicated description isomitted.

As a result, the engine E is stopped when the number Ne of revolutionsof the engine is decreased to the number of idling-revolutions of theengine by prohibiting the restarting of the fuel supply subsequent tothe fuel cut by the fuel supply control means 6. On the other hand, ifthe capacitor remaining-capacity determining flag F_FCMGCAP has been setat “0” at Step S37, it is determined that the remaining capacity is notsufficient to restart the engine E, and at Step S33, the idle enginestop control performing flag F_FCMG is set at “0”. As a result, theidling operation is permitted when the number Ne of revolutions of theengine is decreased to the number of idling-revolutions of the engine byrestarting, as usual, the fuel supply subsequent to the fuel cut by thefuel supply control means 6.

As described above, when the clutch switch S₅ is in the turned-off state(the clutch-engaged state), and when the clutch switch S₅ is in theturned-on state (the clutch-disengaged state) and the shift position isthe neutral position, the engine is stopped without being idled.Therefore, the unnecessary idling operation of the engine E can beminimized to reduce the amount of fuel consumed to the maximum. However,as described above, when the vehicle speed V is less than 15 km/hr, whenthe accelerator pedal has been depressed, and when the remainingcapacity of the capacitor 3 is not sufficient to restart the engine E,the carrying-out of the idle engine stop control operation isprohibited.

If the remaining capacity of the capacitor 3 is not sufficient torestart the engine E at Step S37 and at that time, the engine E is inthe stopped state at Step S30, the starter motor 7 is driven at StepS31, whereby the engine E is restarted before being fallen into a statein which it cannot be actually restarted. However, if the clutch is inthe engaged state and the shift position is in the in-gear state, whenthe engine E is restarted, a problem of a large load applied to thestarter motor 7 is encountered.

Therefore, it is determined at Step S38 whether the shift position isthe neutral position or in the in-gear state. If the shift position isin the in-gear state, the engine restarting delay timer tmFCMG is set atStep S40, shifting to Step S33. Thus, it is possible to avoid therestarting of the engine E in the in-gear state at Step S31 and toprevent a large load from being applied to the starter motor 7. Onlywhen the neutral state is continued until a predetermined time (e.g., 2seconds) countered by the engine restarting delay timer tmFCMG islapsed, the restarting of the engine E at Step S31 is permitted even ifthe shift position is the neutral position at Step S39. Thus, only whenthe shift position is reliably neutral, the restarting of the engine Ecan be carried out, and it is possible to prevent an over-load frombeing applied to the starter motor 7.

FIG. 15 shows a time chart illustrating one example of the idle enginestop control operation.

When the driver releases his foot from the accelerator pedal anddepresses the brake pedal at a time point t₁ during cruising of thevehicle, the fuel cut is carried out by the fuel supply control means 6,whereby the vehicle speed V is gradually reduced. If the driverdepresses the clutch pedal 9 to bring the shift position to the neutralposition when the number Ne of revolutions of the engine is near thenumber of idling-revolutions of the engine at time point t₂, the engineE is stopped without being idled, because the idle engine stop controlperforming flag F_FCMG has been already set at “1”, whereby the fuelsupply subsequent to the fuel cut is not restarted. Thereafter, when thedriver depresses the clutch pedal 9 to bring the shift position to thein-gear state at a time point t₃ in order to start the vehicle, the idleengine stop control performing flag F_FCMG is set at “0” and at the sametime, the fuel cut by the fuel supply control means 6 is finished, andthe supplying of fuel is restarted to start the engine E. When theclutch is brought into the engaged state at time point t₄, the vehiclecan be started.

Although the embodiments of the present invention have been described indetail, it will be understood that the present invention is not limitedto the above-described embodiments, and various modifications in designmay be made without departing from the spirit and scope of the inventiondefined in claims.

For example, the hybrid vehicle using the engine E and the motor M astraveling drive sources has been illustrated in the embodiments, but thepresent invention is applicable to vehicles using only an engine E as atraveling drive source.

The automatic transmission Ta in the first embodiment is not limited toa continuous invariable type and may be of a continuous variable type(CVT).

The engine E is stopped without restoring of the fuel supply subsequentto the fuel cut in the embodiment, but a target number of revolutions ofthe engine can be set at a number of revolutions less than the number ofidling-revolutions to stop the engine E. An ignition control can be alsoemployed in addition to the control of the amount of fuel supplied.

The motor for traveling of the vehicle can be utilized as a startermotor without provision of a special starter motor 7 for starting theengine E. Further, the engine starting means in the present invention isnot limited to the starter motor 7 or the motor M, and includes aso-called “intrusion” type for starting the engine using a kineticenergy of the traveling vehicle. What corresponds to this is, forexample, a case where the engine E is restarted at Step S12 in the flowchart in FIG. 8, when the vehicle speed V is less than 15 km/hr at StepS7 in the flow chart in FIG. 7.

The engine starting power source is not limited to the capacitor 3, andmay be a rechargeable battery. In this case, a remaining capacity can becalculated by integrating the charged current and the discharged currentin the battery.

In the cruising/idling mode, the capacitor 3 can be charged by theelectric power generated by the motor M.

What is claimed is:
 1. An engine stop control system for a vehicle,comprising: an engine; an automatic transmission for transmitting adriving force of said engine to driven wheels; a shift positiondetecting means for detecting a shift position of said automatictransmission; a braking operation detecting means for detecting abraking operation provided by a drive; a fuel supply control means forcontrolling the supply of fuel to said engine; a decelerated-statedetecting means for detecting a decelerated state of the vehicle; and anengine output control means including a means for cutting off thesupplying of fuel to said engine by said fuel supply control means whenthe decelerated state of the vehicle is detected by saiddecelerated-state detecting means, and for restarting the supplying offuel to start said engine when the number of revolution is of the engineis equal to or less than a threshold value, said engine output controlmeans operating after cutting-off of the supply of fuel by said fuelsupply control means during deceleration of the vehicle, to restart thesupplying of fuel if the number of revolutions of the engine becomesequal to or less than said threshold value when the shift positiondetected by said shift position detecting means is a travel position andthe braking operation is not detected by said braking operationdetecting means, and to stop said engine without restarting of thesupply of fuel even if the number of revolutions of the engine becomesequal to or less than said threshold value, when the shift positiondetected by said shift position detecting means is a non-travelposition, or when the shift position detected by said shift positiondetecting means is a travel position and the braking operation isdetected by said braking operation detecting means.
 2. An engine stopcontrol system for a vehicle according to claim 1, wherein, afterstopping of the engine, when the shift position detected by said shiftposition detecting means is a travel position and the braking operationis detected by said braking operation detecting means, said engine ismaintained in a stopped state, and when the shift position detected bysaid shift position detecting means is a travel position and the brakingoperation is not detected by said braking operation detecting means, theengine is started.
 3. An engine stop control system for a vehicleaccording to claim 1, wherein when the shift position detected by saidshift position detecting means is a backward travel position afterstopping of the engine, said engine is started.
 4. An engine stopcontrol system for a vehicle according to claim 3, wherein when theshift position detected by said shift position detecting means is saidbackward travel position for a period of time exceeding a predeterminedtime, said engine is started.
 5. An engine stop control system for avehicle according to any of claims 1 to 4, wherein when a remainingcapacity of an engine starting power source is equal to or greater thana predetermined value, said engine is permitted to stop and when theremaining capacity of said engine starting power source is less than thepredetermined value, the stopping of said engine is prohibited, or thestarting of said engine is permitted.
 6. An engine stop control systemfor a vehicle according to claim 1, wherein the cutting-off of thesupply of fuel to said engine is carried out after a vehicle speed oncereaches a predetermined vehicle speed.
 7. An engine stop control systemfor a vehicle according to claim 2, wherein the cutting-off of thesupply of fuel to said engine is carried out after a vehicle speed oncereaches a predetermined vehicle speed.
 8. An engine stop control systemfor a vehicle according to claim 3, wherein the cutting-off of thesupply of fuel to said engine is carried out after a vehicle speed oncereaches a predetermined vehicle speed.
 9. An engine stop control systemfor a vehicle according to claim 4, wherein the cutting-off of thesupply of fuel to said engine is carried out after a vehicle speed oncereaches a predetermined vehicle speed.